This invention relates to biologically pure cultures of microorganisms and, more particularly to strains of a newly discovered thermophilic ethanol forming anaerobe. Further, the invention relates to the preparation of pure cultures of said anaerobe and to a novel process for producing ethanol therefrom.
Relatively few anaerobic microorganisms have been isolated and characterized that grow on carbohydrates (are glycolytic) and yield ethanol under thermophilic and extreme thermophilic conditions. Representative examples of well-characterized glycolytic anaerobic bacteria that will grow in a nutrient culture in the thermophilic to extreme thermophilic ranges belong to the genus Clostridium and include: C. Thermoaceticum, C. tartarivorum, C. thermosaccharolyticum, C. thermocellum, C. thermocellulaseum and C. thermohydrosulfuricum. Strains of the latter have been isolated and characterized by J. Wiegel and L. G. Ljungdahl (See Abstract I 75 of the Abstract of the Annual Meeting of the American Society of Microbiology, Las Vegas, Nev., U.S.A., 1978). A neotype strain of C. thermohydrosulfuricum E 100-69 was isolated from the liquors of an Austrian sugar beet factory by F. Hollaus and U. Sleytr (See Arch. Mikrobiol. 86: 129-146, 1972).
These microorganisms are, of course, of interest for the possible anaerobic fermentation of various carbohydrates, such as saccharides, to assist in combination (mixed cultures) with other bacteria to efficiently break down cellulose, and for the direct production of ethanol and other products of fermentation under thermophilic conditions. Yeast (Saccharomyces species) fermentation of sugar, as is well known, ordinarily must be conducted at less than about 37.degree. C. under semiaerobic conditions to yield ethanol. Further, the conditions must be carefully controlled to avoid contamination of harmful bacteria, fungi, and molds.
In the isolation of thermophilic anaerobic bacteria, in particular, Clostridium species, from mud samples from the hot springs at various locations in Yellowstone National Park, U.S.A., two strains of a new anaerobic thermophilic glycolytic species have been discovered. In the isolation, purification and characterization of this newly discovered species, which is not a Clostridium, it has been found that the new species is an efficient producer of ethanol from various carbohydrates, in particular, the most common mono- and di-saccharides. As is disclosed and claimed in a copending application, Ser. No. 074,086, filed on the same date by the same inventors, the newly discovered species disclosed herein is also useful in mixed nutrient cultures (i.e., with certain Clostridia species) for the production of ethanol from cellulose.